1. Field of the Invention
The invention relates to a control lever assembly for actuating a control cable, particularly a cable capable of transmitting compressive forces as well as tensile forces, commonly called a push-pull cable, which has applications in the marine control industry.
2. Prior Art
Control heads for controlling devices remotely have been used for many years in the marine industry, for example, for controlling an engine and gearbox of a marine vessel. Bowden cables have been used successfully in certain applications, the Bowden cable having a sheath and a cable core slidable within the sheath. The core is relatively flexible and thus is prone to buckling when subjected to compressive forces, and preferably this type of cable is used only in situations where it is subjected to a tensile force.
The limitations of the Bowden cable to transmitting force in one direction, namely as a tensile force, have been recognized for many years and now a cable having a stiffer core has been developed, such cable being known as a push-pull cable which is capable of carrying a degree of compressive forces before buckling when extending from an end of the sheath and being unsupported by the sheath. The tendency of a push-pull cable to buckle under compressive force is proportional to the length of unsupported core extending from the sheath, and also, to some extent, the alignment of the sheath with the core itself and the line of action and direction of the compressive force applied to the core. Commonly, a core of cable is anchored to a rotatable member at a position spaced from the axis of rotation thereof so that as the member is rotated the core anchoring means, and with it the core, is subjected to swinging and lateral movement which shifts the cable core from a position aligned with an adjacent end portion of the sheath. To reduce buckling and binding tendencies of the sheath on the core, the adjacent end of the sheath swivels to accomodate the lateral swinging of the core. This is attained by several diffent methods in the prior art, for example, see U.S. Pat. No. 2,975,653 (Morse) and U.S. Pat. No. 3,101,821 (Henry). In both of these prior art structures, an adjacent end portion of the sheath enclosing the core is swung laterally by direct movement of the core itself acting on the sheath, which swivels on a sheath swivelling connection. Whilst this arrangement is satisfactory for some applications, where there is a relatively long length of unsupported core extending from the outer portion of the sheath to the core connection and a compressive force is applied to the core, as in the pushing mode, buckling of the core can result due to the inability of the sheath to follow wide swings of the core and to become aligned therewith.